1. Field of the Invention
The present invention relates generally to motor pulleys for overlock sewing machines and, more particularly, to a motor pulley for an overlock sewing machine which is configured such that the flow rate of air which is blown from the pulley to a motor side of the overlock sewing machine is markedly increased, and which has an improved path of air flow, thus reducing a loss of air flow and increasing the flow rate of air.
2. Description of the Related Art
Generally, an overlock sewing machine is a sewing machine which sews over the edge of cloth to prevent it from running. The overlock sewing machine needs a motor pulley for cooling elements, such as a motor, a frame, an oil pan, etc., of the sewing machine, because the sewing speed of the sewing machine is comparatively high.
FIG. 1 shows an example of a conventional motor pulley. Fan blades 2 are integrally provided in a frame 1 of a handwheel. A metal shaft sleeve 4 which is coupled to the output shaft of a motor is fitted into a core part 3 of the handwheel. The fan blades 2 are integrally formed with the frame 1 by injection molding.
In the conventional motor pulley having the above-mentioned construction, the effect of dissipating heat generated from the motor can be improved by providing the fan on the handwheel frame 1. In addition, because the fan blades 2 and the handwheel frame 1 are integrally formed by injection molding, the process of manufacturing the motor pulley is simple, and the production cost can be reduced.
However, the conventional motor pulley, having the effect of dissipating heat of the motor adjacent to the pulley, is problematic in that the area of direct contact that the air blown from the pulley makes with the oil pan and the outer wall of the apparatus is reduced, because the pulley blows air to the outside of the apparatus. In the case of a cooling system of an overlock machine in which oil of the oil pan is dispersed by an oil pump into the apparatus, the cooling efficiency is lowered.
Meanwhile, FIG. 2 illustrates a motor pulley according to another conventional technique. The motor pulley of FIG. 2 is a closed pulley with radial ribs and is configured such that air is sent to a motor side by the ribs 12 provided in the pulley 10 when rotating. A metal shaft sleeve 14 which is coupled to the output shaft of the motor is fitted into a core part of the pulley 10. The ribs 12 are integrally formed with the pulley 10 by injection molding.
In this conventional motor pulley, the motor is cooled by the radial ribs 12. The motor pulley is a closed shape so that outside impurities are prevented from entering the pulley.
However, because the pulley does not provide a path along which to draw outside air into the pulley, an air eddy phenomenon is caused inside the pulley, thus reducing the flow rate of air blown from the pulley.
Further, although this conventional motor pulley could be effective at cooling a motor of a low-speed sewing machine, the cooling efficiency is lowered in an oil scattering cooling system of a high-speed sewing machine, such as an overlock sewing machine, because the flow rate of air is comparatively low.
FIG. 3 illustrates a conventional open pulley with radial ribs 22, configured such that air is sent to a motor side by the ribs 22 provided in the pulley when rotating. This pulley has additional slots 24 so that outside air is drawn into the pulley.
This conventional motor pulley cools the motor using the radial ribs 22, has the slots 24 to mitigate an air eddy phenomenon, and increases the flow rate of air that enters the pulley, thus enhancing the flow rate of air that is blown from the pulley to the motor.
However, in this conventional motor pulley, because the ribs 22 are arranged in radial directions around the axis of the pulley to be aligned with the axis of the pulley, as shown in FIG. 4, the direction of air flow is oriented outwards rather than being oriented towards the central axis of pulley. Thus, the flow rate of air that is blown from the pulley is limited. Therefore, a motor pulley has been required, which exhibits satisfactory cooling efficiency even in an oil dispersing cooling system of a high-speed sewing machine, such as an overlock sewing machine.